DESCRIPTION: Bacterial cell division is a complex, highly regulated process in which biosynthesis of the cell envelope components is reoriented to form a division septum. The process is regulated both temporally and spatially, to ensure equal partitioning of cellular components including a copy of the bacterial chromosome. Septum formation must involve coordinated synthesis of cell wall and cell membrane components of the cell envelope. The chemical nature of the bacterial cell septation site remains one of the most significant unanswered questions remaining in procaryotic biology. The highly conserved nature of the bacterial cell division apparatus makes this process a likely target for the development of future antibacterial chemotherapeutic agents. The project involves a molecular genetic characterization of two minicell determinants (minC and divlVA) and three cell shape determinants (mreBCD) of the Gram-positive bacterium Bacillus subtilis. The sites of action of these proteins in the bacterial cell will be examined by immunofluorescence techniques. The minicell genes encode proteins which are the earliest known acting proteins involved in the process of bacterial cell division. Therefore, they target the nascent septation site before the bulk of the cell division proteins become involved in the process. Sites on the minicelling-associated proteins which are involved in the localization of the proteins to the septation site will be identified. The DivlVA protein is known to be involved in the process of endospore formation in this bacterium, a process which involves an asymmetric septation event. The nature of the interface between the DivlVA cell division protein and the bacterial sporulation machinery will be examined. The mre cell shape determination genes encode proteins which affect cell morphology through their involvement in the cell division process. The MreC protein has been shown to be localized at the division septa in exponentially growing cells of B. subtilis. The roles of the MreB, MreC, and MreD proteins in the division process will be studied. Through the isolation of suppressor mutations, proteins which interact with the Mre proteins will be identified.